Macroinvertebrate seedbank survival in pristine and nutrient-enriched intermittent streams and its contribution to flow phase communities

Abstract

Intermittent stream research focuses mostly on pristine streams. The impacts of nutrient enrichment on invertebrate communities in these systems thus remains underexplored, especially in temperate climates. This study aimed to compare taxa survival during stream drying within pristine and nutrient-enriched sediment streambeds and to evaluate seedbank contribution for community recovery. Ten dry sediment subsamples were each collected from three streams of each nutrient status type. These were rehydrated for 60 days in laboratory with persisting and hatching invertebrates being recorded. Oligochaetes and molluscs were the most abundant; stoneflies and mayflies were common; caddisflies were represented by only a few specimens. The seedbank comprised of around one-third of taxa recorded during flow phases with slightly higher taxa numbers in nutrient-enriched streams. Moisture content positively affected seedbank taxa richness, while dry period duration decreased it. Taxa richness has a unimodal response to nutrient enrichment, with fine sediment proportion revealing no significant effect. Our results show a richer macroinvertebrate seedbank in drying sediments under moist conditions with mild nutrient enrichment, while raised nutrient levels limited macroinvertebrate survival. These results highlight the crucial role of seedbanks in community recovery of intermittent temperate streams, which will become more common with climate change.